Many wrenches known in the art have had jaws that approach a nut or bolt while being at an angle to each other. This is damaging to the nuts and bolts of good machinery. To overcome this problem the art has developed wrenches having jaw surfaces which move in parallel toward a nut for engaging the flat sides of the nut over broad areas. Parallel jaw adjustable wrenches of the past have operated by the manipulation of worm gears. Such wrenches have a looseness and tend to slip off of a nut while great wrenching pressure is being applied. The sudden release of pressure causes an operator's hand to fly through the air, often cutting the operator's knuckles on adjacent machinery. Consequently, these wrenches are nick-named "knuckle-busters". Thus, there is a need for a wrench which has the advantages of parallel jaws combined with the high gripping.
Most nuts for which wrenches are used today have either a square or hexagonal shape. A hexagonal nut has two surfaces at each corner that lie in planes 120 degrees apart. For that reason wrenches which have a handle at a 30 degree angle relative to the jaws are more effective. This angle also permits the wrench to be used more easily on nuts which are in such tight spots that a 60 degree wrenching stroke is not possible.
In my U.S. Pat. No. 5,289,746, issued Mar. 1, 1994, I disclose a parallel jaw toggle wrench that has a first jaw fixed to a handle and a second sliding jaw slidable toward and away from the fixed jaw. The first and second jaws have parallel pressure surfaces disposed at an angle of thirty degrees with respect to the elongation of the handle. A link is pivotally mounted to the forward end of the lever and has a forward end pivotally attached to the sliding jaw. A carrier is moved along the handle by a manually controllable adjustment assembly mounted on the rearward end of the handle. The lever is pivotally attached to the carrier, rearward of the link. A movement of the rearward end of the link toward the fixed jaw side of the handle, causes forward movement of the link for toggle-pressing the sliding jaw toward the fixed jaw. In that wrench the jaws are biased to an open position by a spring extending between the lower jaw and the handle. Such a configuration requires that the wrench body be shaped differently from popular wrenches used by mechanics.